Apparatuses and methods for detecting wave front abberation of projection objective system in photolithography machine

Abstract

Apparatus and methods for detecting wave front aberration of a projection objective lens in a photolithography machine are disclosed. The apparatus comprises: a light source system configured to generate an illuminating beam; a spatial filter configured to receive the illuminating beam and generate ideal spherical wave; a splitter plate arranged downstream to the spatial filter at a predetermined angle with respect to an optical axis of the spherical wave and having a transflective film being applied on a surface thereof; the projection objective lens configured to receive a beam from the splitter plate and generate an output beam; a spherical mirror configured to reflect the output beam from the projection objective lens to the projection objective lens, light passing through the projection objective lens being reflected by the splitter plate; and an interferometer configured to receive light reflected by the splitter plate and measure the wave front aberration of the projection objective lens.

What is claimed is: 
     
       1. An apparatus for detecting wave front aberration of a projection objectNe lens in a photolithography machine, comprising:
 a light source system configured to generate an illuminating beam; 
 a spatial filter configured to receive the illuminating beam and to generate an ideal spherical wave; 
 a splitter plate arranged downstream to the spatial filter at a predetermined angle with respect to an optical axis of the spherical wave and having a transflective film being applied on a surface thereof; 
 a projection objective lens configured to receive a beam from the splitter plate and generate an output beam; 
 a spherical mirror configured to reflect the output beam from the projection objective lens to the projection objective lens, light passing through the projection objective lens being reflected by the splitter plate; and 
 an interferometer configured to receive light reflected by the splitter plate and measure the wave front aberration of the projection objective lens, 
 wherein the interferometer comprises: 
 a beam divider device configured to diffract the light reflected by the splitter plate, the beam divider device being constituted by two one-dimensional binary amplitude gratings or two one-dimensional binary phase gratings having orthogonal reticle directions; 
 an image-plane spatial filter arranged downstream to the beam divider and having windows allowing predetermined orders of diffraction light; 
 a data collection unit configured to collect interference patterns of light passing through the windows; 
 a computer configured to process the collected interference pattern data to obtain the wave front aberration, and 
 a stage configured to carry the two one-dimensional binary amplitude gratings or two one-dimensional binary phase gratings and to move in two dimensional directions precisely. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the predetermined angle is in a range of 30 to 60 degrees. 
     
     
       3. The apparatus according to  claim 1 , wherein the image-plane spatial filter allows +1 order and −1 order of diffraction light to pass through. 
     
     
       4. The apparatus according to  claim 1 , wherein the projection objective lens is a transmissive projection objective lens, a transflective projection objective lens, or a reflective projection objective lens. 
     
     
       5. The apparatus according to  claim 1 , wherein there is immersive liquid between a surface of the projection objective lens and the spherical mirror. 
     
     
       6. A method for detecting wave front aberration of a projection
 objective lens in a photolithography machine, comprising: generating an illuminating beam; generating an ideal spherical wave from the illuminating beam; 
 providing a splitter plate arranged at a predetermined angle with respect to an optical axis 
 of the spherical wave and having a transflective film being applied on a surface thereof; projecting a beam from the splitter plate to the projection objective lens; reflecting an output beam from the projection objective lens to the projection objective lens, and then reflecting light passing through the projection objective lens by the splitter plate; and 
 receiving light reflected by the splitter plate and measuring the wave front aberration of the projection objective lens, 
 wherein the measuring comprises: 
 diffracting the light reflected by the splitter plate by a beam divider device, the beam divider device being constituted by two one-dimensional binary amplitude gratings or two one-dimensional binary phase gratings having orthogonal reticle directions; 
 filtering diffraction light from the beam divider device to allow predetermined orders of diffraction light through windows in an image-plane spatial filter; 
 collecting interference patterns of light passing through the windows; and processing the collected interference pattern data to obtain the wave front aberration˜ 
 wherein the two one-dimensional binary amplitude gratings or two one-dimensional binary phase gratings are moved in two dimensional directions precisely. 
 
     
     
       7. The method according to  claim 6 , wherein the predetermined angle is in a range of 30 to 60 degrees. 
     
     
       8. The method according to  claim 6 , wherein the predetermined order is +1 order and −1 order. 
     
     
       9. The method according to  claim 6 , wherein the projection objective lens is a transmissive projection objective lens, a transflective projection objective lens, or a reflective projection objective lens. 
     
     
       10. The method according to  claim 6 , wherein there is immersive liquid between a surface of the projection objective lens and the spherical mirror.